Field of the Invention
One disclosed aspect of the embodiments relates, for example, to a driving circuit for a vibration type actuator, a vibration device, an image blur correction apparatus, a replacement lens, an image pickup apparatus, and an automatic stage.
Description of the Related Art
A vibration type motor is an example of a vibration type actuator and includes an elastic member, a vibrator including an electric-mechanical energy conversion element such as a piezoelectric element coupled to the elastic member, and a driven member in pressure contact with the vibrator. The vibration type motor is a non-electromagnetic driving system motor arranged to apply an alternating-current (AC) voltage to the electric-mechanical energy conversion element to generate a high-frequency vibration in the element and take out the vibration energy as a continuous machine motion.
A control apparatus for the vibration type actuator includes a pulse signal generation unit configured to generate a pulse signal and a booster circuit configured to apply the amplified AC voltage to a piezoelectric element included in the vibrator. A speed of the vibration type actuator can be controlled on the basis of a frequency, an amplitude, a phase difference, or the like of the AC voltage applied to the piezoelectric element, and the vibration type actuator is used, for example, for autofocus driving of a camera or the like. The autofocus driving needs highly accurate positioning control, and position feedback control using a position sensor is performed, for example.
At the time of control, by using a phenomenon that a vibration amplitude is increased as a driving frequency is closer to a resonance frequency of a driving vibration mode of the piezoelectric element, and the vibration amplitude is decreased as the driving frequency is farther away from the resonance frequency towards a high-pass side, a lens corresponding to a driving target object is driven at a high speed or a low speed.
At this time, in a case where a speed range is desired to be widely extended from an ultralow speed to a high speed, a used driving frequency range needs to be extended. However, in a case where the driving frequency range is extended, an unwanted vibration mode corresponding to a vibration mode that is not used for driving of the vibration type actuator is excited, and abnormal noise may be generated.
Descriptions will be given of the unwanted vibration. Although depending on a model of the vibration type motor, the unwanted vibration mode exists in a frequency that is twice, three times, or ½ times as high as the driving frequency or its intermediate or the like. With the application of the AC voltage to the vibration type actuator, a vibration wave for exciting a driving unit of the vibrator to cause an elliptical motion is generated, and the driven member and the vibrator contact with each other, so that a relative position of the vibrator and the driven member changes in a linear direction or a rotation direction. During the driving of the vibration type actuator, a contact pressure at a contact unit is ideally regularly constant, but in actuality, the contact pressure is varied due to irregularities of a contact surface of the driving unit and the driven member and is also changed depending on a contact position. That is, in a case where the contact pressure is changed during the driving and a vibration mode other than the vibration used for the driving is generated, the unwanted vibration randomly occurs in the vibrator at a frequency that is different from the driving frequency. The unwanted vibration disturbs a driving efficiency and also may be a cause of the generation of the abnormal noise.
The following method is proposed to address this matter. According to a technology described in Japanese Patent Laid-Open No. 03-032374, an impedance element is provided in parallel to an electrostatic capacitance of the piezoelectric element to form a closed circuit, and a parallel resonance frequency is matched to a vibration frequency of a fixed member. A variable coil is used as the impedance element.